Agriculture and Food 7–12 · Years 9–10

Germination test, thousand grain weight and the sowing rate

Plant Production 1

Practical, model not builtLow risk

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The idea

The mass of seed to sow per hectare depends on the target plant density, the seed size (thousand grain weight) and the fraction of seeds that germinate and establish, so a germination count changes the sowing rate.

What you need

untreated wheat or barley seed from two seed lots, about 1500 seeds per lot
paper towel, clear plastic bags and rubber bands for rolled-towel germination
balance reading to 0.1 g (a kitchen scale reading to 1 g is enough for thousand grain weight)
counting board or tray
water spray bottle

How to do it

Count four replicates of 100 seeds from each lot, lay each on a wet paper towel, roll it loosely, put it upright in a plastic bag and keep it at room temperature.
After 7 days unroll the towels and count seedlings with a healthy root and shoot; record abnormal and ungerminated seeds separately.
Calculate germination percentage for each replicate and the lot mean.
Count 1000 grains of each lot and weigh them: this is the thousand grain weight in grams.
Use the model to calculate the sowing rate needed for a target plant density (the BCG table gives wheat targets of 150–220 plants per square metre depending on rainfall zone), first with germination only and then with an establishment percentage as well.
Calculate how many plants per square metre each lot would give at one fixed sowing rate, and explain why sowing by mass alone is not enough.

What you should see

Replicates of 100 seeds from one lot give similar germination percentages, and a lower germination lot needs proportionally more seed. With the Birchip Cropping Group formula, a 40 g thousand grain weight, 150 plants per square metre and 80% establishment give 75 kg/ha; a 24 g lot needs only 45 kg/ha for the same target. Including 95% germination with 80% field establishment raises the 40 g lot to 78.9 kg/ha. The learner knows it worked when the calculated rates differ between the two lots in proportion to their seed weights and germination percentages.

What changes

What you change: seed lot
What you measure: germination percentage, thousand grain weight (g), calculated sowing rate (kg/ha)
What you keep the same: 100 seeds per replicate
same towel moisture and temperature
7-day count
same counting rules

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A kilogram of seed gives the same number of plants whatever the variety.
Every seed sown becomes a plant.
Sowing more seed always gives a bigger yield.

Safety card

Low riskLearners carry it out

Hazards

farm-saved seed may be treated (pickled) with fungicide
grain dust

Controls

use untreated seed, or gloves and hand washing if only treated seed is available
treated seed never enters the food room

Note

Seed dressings are pesticides: follow the product label and NSW Department of Education, Chemical Safety in Schools (CSIS) 2021 Technical Update: Section 1 (general information for all staff) and Volume 2 Appendix D (generic risk assessment advice for each chemical). Complete a CSIS or RiskAssess site-specific risk assessment before the lesson.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Agricultural Technology Years 7–10 Syllabus (2019)AG5-6 AG5-11 AG5-12
Agriculture Technology 7–10 Syllabus (2024), new syllabus, implementation from 2027AGT5-USE-01
Australian Curriculum v9AC9TDE10K04AC9S10I03

Sources

The pages the author read to write this activity.

All Concept Studio activities